The goal of this clinical trial is to compare two different, market approved, cryoballoon devices for the treatment of paroxysmal atrial fibrillation (AF).

The main aims of the study are:

• to compare the efficacy of two ablation devices (acute and 1 year success rates)
• to compare the procedural characteristics (procedure duration, fluoroscopy duration, ablation time
• to compare the complication rates

Participants who have indication for cryoballoon ablation of AF will be randomized in 1:1 fashion to older fixed size cryoballoon and newer expandable cryoballoon. Standard of care cryoballoon procedure will be performed alongside with standard postprocedural follow-up.

• to compare the complication rates

Participants who have indication for cryoballoon ablation of AF will be randomized in 1:1 fashion to older fixed size cryoballoon and newer expandable cryoballoon.

Patients suffering from paroxysmal atrial fibrillation who are scheduled (independently of this study) for cryoballoon pulmonary vein isolation will be informed about the study and potential risks. All patients who give written informed consent will be randomized to 4th generation Artic Front Advance Pro device (fixed size balloon of 28 mm) and Polar X Fit device (28-31 mm expandable balloon). The ablation procedure will be performed in standard of care fashion. Also, standard postprocedural follow up of the patients will be scheduled with outpatient clinic visits and 24-hour Holters and 3, 6 and 12 months, and yearly thereafter. Extra visits will be scheduled in the case of symptoms/palpitations.

Standard patient and procedural data will be collected alongside with the information obtained in the follow up.

Inclusion Criteria:

• paroxysmal atrial fibrillation
• patient scheduled for cryoballoon pulmonary vein isolation regardless of this study

Exclusion Criteria:

• unwilling to sing the informed consent Left atrium size > 55 mm Uncontrolled heart failure (NYHA III-IV) Intracardiac thrombi